need back up disk

The first problem we encountered was black screen and even though we tried some things that we learned from youtube it did'nt improve. No parts were replaced and instead of worrying about it we just hooked it to a desktop monitor and that solved our visual problem. Months later we encountered an error that said something about corrupted or missing data. I had the whole thing written down but now I can't find it. The message said sothing about running a cd and pressing R (I think it stands for repair) . I did some googling and the solutions I read about also require the disk that the laptop came with. We don have that cd. Any advice? Thanks.